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Fixture performance improvement by an accelerated integral method of fixture layout and clamping force plan

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 2013年第12期227卷 1819 - 1829页

作者： Liu Zhihui Michael Yu Wang Wang Kedian Mei Xuesong School of Mechanical Engineering Xi’an Jiaotong University Xi’an P. R. China School of Mechanical Engineering Xi’an Jiaotong University Xi’an P. R. ChinaComputational Modeling and Design Laboratory The Chinese University of Hong Kong New Territories Hong Kong

Deformation under external and clamping forces is an important factor affecting fixture performance. To reduce the deformation of the workpiece–fixture system and improve the performance of the fixture, an optimisation method for the fixture layout and clamping force plan is constructed in this article. First, the workpiece–fixture is illustrated as an elastic–elastic contact model with friction in which the workpiece is modelled by the finite element model, while the fixel can be modelled by either the spring model or finite element model. To accelerate the computing speed of solving the contact problem, a matrix size reducing method for the finite element model stiffness matrix is proposed, utilising less computer memory. Based on the same idea, a clamping force optimisation method considering the friction effect is presented to achieve the optimal clamping force of a special fixture layout within very few finite element model computing processes. Then, based on these, an integral fixture layout and clamping force optimisation algorithm are built by genetic algorithm. At the end of this article, numerical examples are taken to prove the performance of the methods. The results show that the accelerating method yields sufficient performance, and the optimisation algorithms of both the clamping force plan and the fixture layout design achieve favourable convergence.

关键词： Fixture layout force–deformation clamping force optimisation algorithm

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Optimum seeking-based non-linear controller to maximise energy capture in a variable speed wind turbine

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IET CONTROL THEORY AND APPLICATIONS 2012年第4期6卷 526-532页

作者： Iyasere, E. Salah, M. Dawson, D. Wagner, J. Tatlicioglu, E. Clemson Univ Coll Engn & Sci Clemson SC 29631 USA Hashemite Univ Dept Mechatron Engn Zarqa Jordan Izmir Inst Technol Dept Elect & Elect Engn Izmir Turkey

In this study, an optimum seeking-based robust non-linear controller is proposed to maximise wind energy captured by variable speed wind turbines at low-to-medium wind speeds. The proposed strategy simultaneously controls the blade pitch angle and tip-speed ratio, through the turbine rotor angular speed, to an optimal point at which the power coefficient, and hence the wind turbine efficiency, is maximum. The optimal points are given to the controller by an optimisation algorithm that seeks the unknown optimal blade pitch angle and rotor speed. The control method allows for aerodynamic rotor power maximisation without exact knowledge of the wind turbine model. A representative numerical simulation is presented to show that the wind turbine can be accurately controlled to achieve maximum energy capture.

关键词： blade pitch angle control wind power optimisation techniques optimisation wind energy capture maximisation wind turbines variable speed wind turbine Power and plant engineering (mechanical engineering) Control of electric power systems aerodynamics Numerical analysis optimisation algorithm numerical simulation Mechanical components Stability in control theory Wind power plants angular velocity control numerical analysis Nonlinear control systems wind turbine efficiency turbine rotor angular speed power generation control power coefficient tip-speed ratio robust control Velocity, acceleration and rotation control nonlinear control systems aerodynamic rotor power maximisation blades low-to-medium wind speed optimisation Fluid mechanics and aerodynamics (mechanical engineering) optimum seeking based robust nonlinear controller rotors

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Optimal data aggregation tree in wireless sensor networks based on intelligent water drops algorithm

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IET WIRELESS SENSOR SYSTEMS 2012年第3期2卷 282-292页

作者： Hoang, D. Chinh Kumar, R. Panda, S. Kumar Natl Univ Singapore Dept Elect & Comp Engn 4Engn Dr 3 Singapore 117576 Singapore

Energy conservation is an important aspect in wireless sensor networks (WSNs) to extend the network lifetime. In order to obtain energy- efficient data transmission within the network, sensor nodes can be organised into an optimal data aggregation tree with optimally selected aggregation nodes to transfer data. Various nature- inspired optimisation methods have been shown to outperform conventional methods when solving this problem in a distributed manner, that is, each sensor node makes its own decision on routing the data. In this study, a novel optimisation algorithm called intelligent water drops (IWDs) is adopted to construct the optimal data aggregation trees for the WSNs. Further enhancement of the basic IWD algorithm is proposed to improve the construction of the tree by attempting to increase the probability of selecting optimum aggregation nodes. The computational experiment results show that the IWD algorithm is able to obtain a better data aggregation tree with a smaller number of edges representing direct communication between two nodes when compared with the well- known optimisation method such as ant colony optimisation. In addition, the proposed improved version of the IWD algorithm provides better performance in comparison with the basic IWD algorithm for saving the energy of WSNs.

关键词： WSN Communication network design, planning and routing Reliability optimisation algorithm optimal data aggregation tree intelligent water drops algorithm telecommunication network routing well-known optimisation method optimisation techniques Sensing devices and transducers computational experiment data routing probability energy conservation Wireless sensor networks optimally selected aggregation nodes energy-efficient data transmission Combinatorial mathematics sensor nodes trees (mathematics) direct communication IWD algorithm nature-inspired optimisation methods wireless sensor networks ant colony optimisation conventional methods network lifetime telecommunication network reliability Other topics in statistics

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A hybrid method for the nondestructive evaluation of the axial load in structural tie-rods

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NONDESTRUCTIVE TESTING AND EVALUATION 2011年第2期26卷 197-208页

作者： Garziera, R. Amabili, M. Collini, L. Univ Parma Dipartimento Ingn Ind I-43100 Parma Italy McGill Univ Dept Mech Engn Montreal PQ Canada

The knowledge of tensile load in reinforcement tie-rods is of crucial importance to assure structural integrity and safety. This work addresses the problem of identifying this tensile load in structural tie-rods of ancient masonry arches and vaults. The proposed procedure is a nondestructive and non-invasive method. It consists in matching the first six natural frequencies of the tie-rod, acquired by a classical accelerometer, with numerically obtained frequencies. This matching procedure is accomplished by an optimisation algorithm in which the length of the rod, the presence of concentrated masses along it and an elastic foundation at the edges are the optimisation variables. In this way, the main unknown, i.e. the axial load, is determined by a mathematical algorithm that automatically minimises the difference between experimental and numerical results on the basis of the choice of multiple parameter combinations. A 'local zoom technique' is adopted around a parameter set, which gives a minimum, in order to determine the load with good approximation. A deep investigation about the stress state in the tie-rods is also carried out via a nonlinear finite element analysis.

关键词： tie-rods vibration-based diagnostics parametric study optimisation algorithm

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Selection of priority areas for arthropod conservation in the Azores archipelago

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JOURNAL OF INSECT CONSERVATION 2011年第5期15卷 671-684页

作者： Gaspar, Clara Gaston, Kevin J. Borges, Paulo A. V. Cardoso, Pedro Univ Acores Azorean Biodivers Grp CITA A Dept Ciencias Agr P-9701851 Terceira Azores Portugal Univ Sheffield Dept Anim & Plant Sci Biodivers & Macroecol Grp Sheffield S10 2TN S Yorkshire England Smithsonian Inst Natl Museum Nat Hist Washington DC 20013 USA

The largest standardised database available to date for arthropods in native forests of the Azores archipelago was used to determine the minimum optimal set of native forest fragments needed to accomplish four different targets of species occurrence (presence-absence) and abundance (20, 50 and 80%) using different groups of arthropods and all data combined. The results showed that occurrence and 20% abundance targets gave similar optimal solutions for most of the groups considered. At least one fragment on each of the seven studied islands was required to accomplish any occurrence and abundance target. To achieve 80% of abundance for all species, all fragments were necessary and to guarantee 50% of the overall abundance of endemics, 17 out of 18 native forests were needed. A suggestion is made to apply a measure of biotic integrity related to disturbance to select, among alternative optimal solutions, the set of areas that will help to guarantee the viability of populations. Some guidelines for the selection of priority areas for conservation in the Azores are presented.

关键词： Arthropods Azores Complementarity Irreplaceability optimisation algorithm Reserve selection

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Automatic tuning method for the design of supplementary damping controllers for flexible alternating current transmission system devices

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IET GENERATION TRANSMISSION & DISTRIBUTION 2009年第10期3卷 919-929页

作者： de Oliveira, R. V. Kuiava, R. Ramos, R. A. Bretas, N. G. Fed Technol Univ Parana Electromech Engn Dept BR-85503390 Pato Branco PR Brazil Univ Sao Paulo Engn Sch Sao Carlos BR-13566590 Sao Carlos SP Brazil

The design of supplementary damping controllers to mitigate the effects of electromechanical oscillations in power systems is a highly complex and time-consuming process, which requires a significant amount of knowledge from the part of the designer. In this study, the authors propose an automatic technique that takes the burden of tuning the controller parameters away from the power engineer and places it on the computer. Unlike other approaches that do the same based on robust control theories or evolutionary computing techniques, our proposed procedure uses an optimisation algorithm that works over a formulation of the classical tuning problem in terms of bilinear matrix inequalities. Using this formulation, it is possible to apply linear matrix inequality solvers to find a solution to the tuning problem via an iterative process, with the advantage that these solvers are widely available and have well-known convergence properties. The proposed algorithm is applied to tune the parameters of supplementary controllers for thyristor controlled series capacitors placed in the New England/New York benchmark test system, aiming at the improvement of the damping factor of inter-area modes, under several different operating conditions. The results of the linear analysis are validated by non-linear simulation and demonstrate the effectiveness of the proposed procedure.

关键词： electromechanical oscillations Control of electric power systems New England-New York benchmark test system Linear algebra (numerical analysis) iterative methods optimisation techniques flexible AC transmission systems a.c. transmission linear matrix inequalities Power convertors and power supplies to apparatus Power system control linear matrix inequality supplementary damping controller design automatic tuning method damping flexible alternating current transmission system device thyristor controlled series capacitors Control system analysis and synthesis methods optimisation algorithm optimisation Interpolation and function approximation (numerical analysis) control system synthesis Control engineering computing power engineering computing bilinear matrix inequality iterative process power transmission control Power engineering computing power capacitors thyristor applications power systems

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An optimisation algorithm for determination of treatment margins around moving and deformable targets

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RADIOTHERAPY AND ONCOLOGY 2005年第2期77卷 194-201页

作者： Redpath, AT Muren, LP Western Gen Hosp Directorate Clin Oncol Dept Oncol Phys Edinburgh Midlothian Scotland Univ Bergen Fac Med Inst Med Sect Oncol Bergen Norway Haukeland Univ Hosp Dept Oncol & Med Phys N-5021 Bergen Norway

Purpose: Determining treatment margins for inter-fractional motion of moving and deformable clinical target volumes (CTVs) remains a major challenge. This paper describes and applies an optimisation algorithm designed to derive such margins. Material and methods: The algorithm works by expanding the CTV, as determined from a pre-treatment or planning scan, to enclose the CTV positions observed during treatment. CTV positions during treatment may be obtained using, for example, repeat CT scanning and/or repeat electronic portal imaging (EPI). The algorithm can be applied to both individual patients and to a set of patients. The margins derived will minimise the excess volume outside the envelope that encloses all observed CTV positions (the CTV envelope). Initially, margins are set such that the envelope is more than adequately covered when the planning CTV is expanded. The algorithm uses an iterative method where the margins are sampled randomly and are then either increased or decreased randomly. The algorithm is tested on a set of 19 bladder cancer patients that underwent weekly repeat CT scanning and EPI throughout their treatment course. Results: From repeated runs on individual patients, the algorithm produces margins within a range of +/- 2 mm that lie among the best results found with an exhaustive search approach, and that agree within 3 mm with margins determined by a manual approach on the same data. The algorithm could be used to determine margins to cover any specified geometrical uncertainty, and allows for the determination of reduced margins by relaxing the coverage criteria, for example disregarding extreme CTV positions, or an arbitrarily selected volume fraction of the CTV envelope, and/or patients with extreme geometrical uncertainties. Conclusion: An optimisation approach to margin determination is found to give reproducible results within the accuracy required. The major advantage with this algorithm is that it is completely empirical, and it is

关键词： optimisation algorithm treatment margins non-solid organs organ motion patient set-up errors

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Error resilient video coding with priority data classification using H.264 flexible macroblock ordering

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IET IMAGE PROCESSING 2007年第2期1卷 197-204页

作者： Im, S. K. Pearmain, A. J. Univ London Queen Mary Coll Dept Elect Engn London E1 4NS England

Flexible macroblock ordering (FMO) is a new error resilience feature in the H.264 (MPEG-4 part 10) video coding standard. The paper exploits FMO to offer a new classification algorithm for prioritised video transmission. Instead of using the default mapping structures of FMO, an optimisation algorithm in which the more important macroblocks (MBs) are categorised in a separate slice group (SG), which corresponds to high-priority packets for transmission, is proposed. The importance of each MB is determined based on its eventual influence on picture quality. This is assessed by considering the fact that the successful transmission of an MB not only enhances the quality of the associated pixels, but also improves the quality of its adjacent lost MBs by improving the efficiency of error concealment. It is assumed that the network can offer a prioritised service for successful transmission of the high-priority SG. Based on this, a vulnerability factor for each MB is determined, and a certain proportion of high-vulnerability MBs at each frame to limit the impact of temporal error propagation is intra-updated. It is shown, where the proposed mapping algorithm outperforms the default mappings of the H.264 codec, that this prioritised transmission will improve the subjective and objective video quality in situations with a high probability of transmission errors.

关键词： prioritised video transmission priority data classification mapping algorithm H.264 flexible macroblock ordering FMO Computer vision and image processing techniques Image and video coding error propagation video coding optimisation algorithm image classification video coding standard picture quality Video signal processing MPEG-4 part 10 slice group error resilient video coding vulnerability factor codec

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On the implementation of cellular wave computing methods by hardware learning

On the implementation of cellular wave computing methods by ...

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IEEE International Symposium on Circuits and Systems

作者： Geis, Gunter Gollas, Frank Tetzlaff, Ronald Univ Frankfurt Inst Appl Phys D-6000 Frankfurt Germany

ISBN: (纸本)9781424409204

Adaptive signal processing on Cellular Nonlinear Networks (CNN) based electronic devices is an exciting challenge, which needs a fast and robust parameter adaptation. In this contribution implementations and the analysis of optimisation algorithms will be proposed and discussed using the EyeRIS (TM) hardware system with an embedded ACE16kv2 focal plane processor having 128 x 128 cells. The parameter training performance will be analysed in detail.

关键词： intelligent sensors cellular nonlinear networks optimisation algorithm EyeRIS visual system

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Investigation of the applicability of the dynamic-Q optimisation algorithm to vehicle suspension design

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MATHEMATICAL AND COMPUTER MODELLING 2003年第9-10期37卷 1029-1046页

作者： Els, PS Uys, PE Univ Pretoria Dept Mech & Aeronaut Engn ZA-0002 Pretoria South Africa

To optimise the handling of a vehicle in conjunction with ride comfort is a challenge due to the fact that the suspension features determining these functions tend to oppose one another. The complexity and nonlinearity of the dynamics of suspension systems impose further difficulty. Furthermore, the suspension characteristics imply a large number of variables. The dynamic-Q optimisation method used here in conjunction with the dynamics simulation code DADS is a robust and reliable algorithm particularly suitable for solving engineering optimisation problems. It applies an existing dynamic trajectory optimisation algorithm to successive spherical quadratic approximate subproblems and can be used when analytical functions are not available and only discrete function values can be obtained via numerical simulation of engineering processes. The purpose of this investigation is to determine whether the dynamic-Q method is suitable for optimising the design of a vehicle suspension system modelled in DADS. (C) 2003 Elsevier Science Ltd. All rights reserved.

关键词： optimisation algorithm dynamic-Q suspension ride comfort vehicle handling

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